The present invention relates generally to methods of packaging integrated circuit devices, such as flip chip dice, with externally mounted but integrally packaged fuses. More particularly, the fuses are formed using lead frame lamination techniques.
In a number of electrical components it is desirable to provide fuses to protect against electrical surges. There are currently a number of commercially available fuse styles. One available type of fuse is known as a positive temperature coefficient fuse. A representative positive temperature coefficient (PTC) fuse is illustrated in FIGS. 1(a) and 1(b). As seen in FIG. 1(a), the representative PTC fuse 50 has a top plate (top contact pad) 52 and a bottom plate (bottom contact pad) 54 that are separated by a positive temperature coefficient resistor material 56. The contact pads 52 and 54 each have tabs 57, 59 which are bent down to form wings that define a cavity 61 beneath the bottom contact pad 54.
A die 64, such as a flip chip packaged Zener diode is then attached to the bottom surface of the bottom contact pad within the cavity 61 as best seen in FIG. 1(b). Solder posts 67 are formed on the tips of bent down tabs 57, 59. With this arrangement, the fuse can be mounted on a printed circuit board (or other appropriate substrate) by soldering the tip solder post 67 and the die""s solder bumps 66 to appropriate landings on the printed circuit board.
The described PTC fuses are used in a number of applications. However, they are generally relatively expensive to package. Accordingly, there are continuing efforts to develop improved methods for packaging such fuses.
To achieve the forgoing and other objects and in accordance with the purpose of the invention, an improved method of packaging external fuses together with integrated circuit devices is described. A pair of frame strips are provided that each have an associated set of contact pads. A resistor paste is applied to one of the contact pad sets and the frame strips are laminated together by curing the resistor paste. The contact pads sets are aligned with one another with the resistor paste there between to form a plurality of fuses. Dice are then mounted on the opposite side of one of the contact pad sets to form integrated circuit devices having integrally packaged external fuses. The packaged devices are eventually singulated for use.
In some embodiments, the contact pads each have downturned tabs that form wings on opposite sides of their associated die. When the dice are flip chips, a device may be attached to a substrate board by soldering bumps on the singulated die and soldering the tab wing tips to the substrate board.
In a preferred embodiment, the resistor paste is a positive temperature coefficient resistor paste.